This invention relates to polymer concrete compositions for use in making corrosion resistant structures and other structural composite elements, as well as methods of making same. Polymer concrete is a term that applies to a variety of composites of polymer and concrete. Such composites can be made by impregnating hardened portland cement with a liquid monomeric material that is subsequently polymerized in situ. Alternatively, they can be made by combining monomeric or polymeric material with a fresh portland cement concrete mixture, both of which are subsequently hardened. Other composites referred to as polymer concrete do not contain cement, per se; rather, they are composites made by polymerizing a monomeric or oligomeric material with filler material, such as aggregate (e.g., gravel, sand, etc.).
Polymer concrete composites have remarkable durability and can have remarkable resistance to salts, acids, and other corrosive materials depending on the formulation. They are, therefore, suitable for use in pipe, tunnel support linings, bridge decks, and corrosion resistant electrolytic containers, for example. The latter represent a significant market for use of polymer concrete composites.
Metals must typically be isolated from mined ores containing the metals. For example, copper must either go through an extraction process to remove copper in pure form, or through refining process in order to eliminate impurities contained in mined copper ores. Electrolytic refining is one of the methods used for refining copper and solvent extraction-electrowinning (SX-EW) is one of the methods used to extract pure copper. In the copper processing industry 85% of the processed copper is obtained by electrolytic refining and the other 15% is obtained by SX-EW. In both the electrolytic refining and the SX-EW processes, copper is extracted from a corrosive electrolytic solution contained in large processing tanks or cells.
The production cost of mineral processing of copper using electrolytic, electrowinning, and SX-EW processing are significantly lower than the cost of processing using mill concentrates, smelting, and refining. For example, production costs for SX-EW and/or electrowinning are significantly lower, averaging a savings of over 60%, than those for copper production via mill concentrates, smelting, and refining. Thus, the technology of solvent extraction-electrowinning (SX-EW) copper production has progressed rapidly over the past five years. It has gained increasing popularity, not only because it is more cost efficient, but also because it is more environmentally acceptable. Further, this technology requires less energy than conventional copper production methods.
The electrolyte solution used in these processes has an acid combination base which is highly corrosive to the material of the container. Various efforts have been made, with limited success, to provide a container which could withstand the highly corrosive environment of the electrolyte solution. Regular replacement and maintenance are needed with the existing containers creating high repair and high replacement cost, causing excessive downtime and lost production.
One way in which the base container has been protected from the corrosive solution is to use a corrosive protective liner, either of hard material or a flexible material, which is placed either over or in the existing container. The container is usually made of a steel-reinforced concrete; however, these concrete containers have been plagued with problems. For example, liners easily leak and vapor and/or mist from the electrolyte solution can penetrate the area between the liner and the concrete container. As a result, the concrete can erode and/or the steel reinforcement can corrode, thereby causing the containers to fail. Such failed containers can be expensive to dispose of because they tend to absorb the highly toxic electrolytic solutions.
Another effort to provide a container which can withstand the highly corrosive environment of the electrolyte solution is through the use of polymer concrete. Typical polymer concrete composites are made from one or more resins, a promoter, and a catalyst to cure the material, along with aggregate. They typically also include fillers such as silica, sand, flour silica, mica flakes, glass spheres, and fiberglass in various sizes. The composite container will sometimes have a gel coat, surface resin and/or a surface veil and mat system to create a corrosive resistant smooth surface.
Although conventional polymer concrete composite containers are a great improvement, they still have many disadvantages. Some of these disadvantages include the high cost of fabrication due to the material costs and manufacturing techniques currently used. Also, conventional polymer concrete composite containers typically require the use of steel reinforcement. Such containers are susceptible to draining electrical current and leaking. There can also be problems with: the formation of cold joints from the casting process causing leaking and leaching paths; irregular interior surfaces creating difficulty in cleaning the container; leaks and leaching sources due to the attachment of overflow and decant boxes, which are cast separately and then attached; the failure of gel coating on the container surface walls in the form of scratches and tears caused by mechanical abuse; poor distribution of solutions in the containers; poor drainage of the solutions from the containers caused by design flaws in the plumbing and mechanical failure of the plumbing; the lack of overall material and/or structural strength in the containers; the failure of hardware and/or plumbing in the container due to mechanical abuse; the difficulty of obtaining consistent specifications and tolerances of the container dimensions; and the consistent leaking and/or leaching of the electrolyte solution through plumbing joints and surface gel coat systems. Leakage can destroy tankhouse floors, short circuit the electrical current, leach into the ground water, disrupt production, and/or threaten the safety of the tankhouse crew. Thus, previous efforts in creating suitable corrosive resistant containers for the electrowinning and/or refining have not been satisfactory.
Therefore, there is a need for polymer concrete composites that can be used in corrosive environments.